The class of magnetic devices encompasses, e.g., magnetic domain or "bubble" devices; encompassed also are magneto-optic devices as described, e.g., by
J. F. Dillon, "The Development of Magneto-optical Research in Garnets and Magnetic Insulators", FERRITES: Proceedings of the International Conference, 1980, pp. 743-749; and by
J. F. Dillon, "Magneto-optics and Its Uses", Journal of Magnetism and Magnetic Materials, Vol. 31-34 (1983), pp. 1-9.
Magneto-optic devices have been receiving increasing attention in connection with optical communications systems which typically include sources, modulators, and detectors of electromagnetic radiation having a specified desired wavelength, and which may further include optical waveguide transmission lines, switches, deflectors, and optical isolators, the latter being intended for preventing spurious reflected light from re-entering a light source. A well-established design for optical isolators is based on Faraday rotation of polarized electromagnetic radiation as mentioned in the above-cited papers and as further described and illustrated by
G. B. Scott et al., "Magneto-optic Properties and Applications of Bismuth-substituted Iron Garnet", IEEE Transactions on Magnetics, Vol. MAG-12 (1976), pp. 292-311; and by
R. C. Booth et al., "Magneto-optic Properties of Rare-earth Iron Garnet Crystals in the Wavelength range 1.1-1.7 micrometer and Their Use in Device Fabrication", Journal of Physics D, Vol. 17 (1984), pp. 579-587.
The latter paper, in particular, is concerned with the magneto-optic properties of a number of single-crystal materials which are classified as rare-earth iron garnets and which incorporate rare-earth elements yttrium, gadolinium, terbium, dysprosium, holmium, erbium, or ytterbium. Faraday rotation data for these and other rare-earth iron garnets, actual and hypothetical, are given by
J. F. Dillon, "Magneto-optical Properties of Magnetic Garnets", Physics of Magnetic Garnets, Societa Italiana di Fisica, 1978; see especially page 399, Table I.
With respect to garnet manufacture it was believed that no unsubstituted rare-earth garnet could form with a lattice parameter greater than 1.2540 nanometer; in this respect see
S. Geller et al., "Magnetic and Crystallographic Study of Neodymium-substituted Yttrium and Gadolinium Iron Garnets", Physical Review, Vol. 123 (1961), pp. 1692-1699; and
G. P. Espinosa, "Crystal-Chemical Study of the Rare-Earth Iron Garnets", Journal of Chemical Physics, Vol. 37 (1962), pp 2344-2347.
Also, magnetic garnets had been made comprising neodymium or praseodymium in amounts not higher than amounts incorporated in respective compounds (Nd.sub.2 Y)Fe.sub.5 O.sub.12 and (Pr.sub.1.8 Y.sub.1.2)Fe.sub.5 O.sub.12. In this respect, see
G. Goldring et al., "On the Incorporation of Neodymium in Mixed Yttrium-Neodymium-Iron Garnets", Journal of Applied Physics, Vol. 31, (1960), pp. 2057-2059; and
P. Hansen et al., Journal of Applied Physics, to appear.